Materials which may, via suitable temperature excursions, be reversibly switched between two structural phases characterized by different resistivities, have the potential to be employed as phase change memory materials. One such class of materials is a material that includes germanium (Ge) and antimony (Sb). Hereinafter the materials including Ge and Sb are referred to as GeSb materials.
In order to fabricate practical memory devices, it will be necessary to deposit the GeSb materials upon substrates of substantial topography complexity. A possible structure for implementing a phase change memory device is a line-and-via structure similar to those found in interconnect wiring structures. In such structures, the phase change material in the narrow via opening would constitute the active element of the memory device.
One promising candidate method for deposition of GeSb materials is chemical vapor deposition. In CVD, numerous organometallic precursors (such as carbonyls, alkyls, etc.) with reasonable vapor pressure exist for a large number of candidate metals. A useful feature of some, but not all, CVD process is selectivity. By this it is meant that the deposition reaction can be carried out such that a material is deposited only on specific underlying materials on the substrate, while not depositing on other materials on the substrate, despite their exposure to the reactant gas at the reaction temperature. Common examples of such CVD process are the selective growth of Si on Si, but with no growth on co-present SiO2 and the growth of W on Si, but also not on SiO2.
The problem to be faced with conventional CVD methods is in performing the deposition at sufficiently low temperature (less than about 400° C.) while still maintaining the desired selectivity mentioned above.
To date, there is no known chemical vapor deposition (CVD) method for depositing GeSb materials onto a substrate at temperatures less than 400° C. having the desired feature of selectivity. As such, there is a need for the development of a chemical vapor deposition method in which the deposition method has the ability to form GeSb materials onto selective areas of a substrate.